Ultrasonic welding is an efficient technique for joining component parts in manufacturing environments. Applications of ultrasonic welding include the welding of plastic parts and fabrics when manufacturing products such as automobile components, medical products, and hygiene products.
Manufacturers who employ ultrasonic welding may use several individual welding devices, or “probes,” in a single manufacturing environment. Individual devices may be customized for particular welds or for use on particular components. It is desirable, from a cost standpoint and also given the motivation to conserve space in a manufacturing environment, to use a minimum of power supplies to power an appropriate number of ultrasonic probes.
To achieve maximum power transfer efficiency (of greater than approximately 90%) from an ultrasonic generator to an ultrasonic load, such as a probe, the generator must drive the ultrasonic load at the load's exact mechanical resonant frequency. Circuitry inside the generator allows the generator drive frequency to track the load resonant frequency, which drifts due to temperature variations and may also be caused by the aging characteristics of the ultrasonic transducer or driver.
Powering more than one ultrasonic load from one ultrasonic generator output at one time can cause an overload condition on the output of the generator, because it is not possible to match the resonant frequency of multiple probes exactly. The resonant frequencies of two probes will change over time because different ultrasonic probes age differently over time and the temperature changes they experience will not match over time. Thus, to power multiple probes from one generator output, the probes should be individually switched to the high voltage (typically greater than 1,000 Vrms) generator output. This may be accomplished by using multiple high-voltage relays, with one relay dedicated to each ultrasonic load.